NZ752542A - Weed inactivation device - Google Patents
Weed inactivation deviceInfo
- Publication number
- NZ752542A NZ752542A NZ752542A NZ75254219A NZ752542A NZ 752542 A NZ752542 A NZ 752542A NZ 752542 A NZ752542 A NZ 752542A NZ 75254219 A NZ75254219 A NZ 75254219A NZ 752542 A NZ752542 A NZ 752542A
- Authority
- NZ
- New Zealand
- Prior art keywords
- voltage
- weed
- current
- inactivation device
- voltage multiplier
- Prior art date
Links
- 241000196324 Embryophyta Species 0.000 title claims abstract description 35
- 230000002779 inactivation Effects 0.000 title claims abstract description 19
- 239000003990 capacitor Substances 0.000 claims description 9
- 230000001939 inductive effect Effects 0.000 claims description 8
- 238000004804 winding Methods 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims 3
- 206010014405 Electrocution Diseases 0.000 claims 1
- 230000001965 increased Effects 0.000 abstract description 5
- 230000004913 activation Effects 0.000 abstract description 4
- 230000002363 herbicidal Effects 0.000 abstract description 4
- 239000004009 herbicide Substances 0.000 abstract description 4
- 230000005284 excitation Effects 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 238000009333 weeding Methods 0.000 description 3
- 238000009413 insulation Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006011 modification reaction Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000001808 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000003467 diminishing Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 230000004301 light adaptation Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Abstract
A weed inactivation device has at least two electrodes, whereby at least one electrode is directed to the weed. The weed activation device is used as a physical herbicide apparatus. A DC or AC power supply of any number of phases generates a voltage. This voltage is fed to an inverter that increases frequency. The current with increased frequency is fed to a harmonic filter. The harmonic filter may feed a high frequency transformer that further increases the voltage input for the voltage multiplier. The output of the previous components is fed to a voltage multiplier, such as a voltage multiplier of the Cockroft-Walton type or a full wave Cockroft-Walten type. The voltage multiplier provides different voltage levels depending on its load, so for a variable load it makes an auto-adjustable power control without any additional circuitry, processor or controller necessity. s frequency. The current with increased frequency is fed to a harmonic filter. The harmonic filter may feed a high frequency transformer that further increases the voltage input for the voltage multiplier. The output of the previous components is fed to a voltage multiplier, such as a voltage multiplier of the Cockroft-Walton type or a full wave Cockroft-Walten type. The voltage multiplier provides different voltage levels depending on its load, so for a variable load it makes an auto-adjustable power control without any additional circuitry, processor or controller necessity.
Description
WEED INACTIVATION DEVICE
CROSS REFERENCE TO RELATED APPLICATIONS
Applicant claims priority under 35 U.S.C. §119 of German Application No. 10
2018 003 199.4 filed April 19, 2018, the disclosure of which is incorporated by
reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to weed inactivation device, comprising at least two
electrodes, whereby the at least one electrode is directed to the weed. The weed
activation device is used as a physical herbicide apparatus.
2. Description of the Related Art
A weed activation device of the generic type has been disclosed in the yet
unpublished international patent application PCT/IB2017001456. According to
PCT/IB2017001456 a high voltage is created by the utilization of high voltage
transformers. The high-voltage in the range of 1 kV to 20 kV is applied to an electrode
which contacts the weed to be controlled or which is brought close to the weed. This
physical herbicide has the great advantage of not utilizing chemical herbicides, which
may proliferate into the food chain up to humans.
SUMMARY OF THE INVENTION
It is an object of the current invention is to provide for a circuitry, which allows
use of small, cheap and available electronic components to comprise a high power-
factor converter that controls for power without the need of software or other larger
components required in previous technological generations. This particular converter is
composed of at least the following components: An inverter, an inductive and or
capacitive harmonic filter, a capacitive voltage multiplier composed of diodes and
capacitors.
Therefore, a weed inactivation device is proposed, comprising at least two
electrodes, whereby the at least one electrode is directed to the weed and is supplied
with electrical energy by at least one electrical power supply. The at least one electrical
power supply could as an example comprise an AC current supply having a frequency
in the range of 30 Hz to 90 Hz, preferably in the range of 50 Hz to 60 Hz, and whereby
the AC current is rectified by a full-wave rectifier, creating pulsed DC current doubling
the AC frequency.
According to the invention a weed activation device is proposed, which is
operated with any power supply available.
The power supply is fed to an inverter such as a full or half bridge inverter to
create a high frequency current of different frequency than the input current. This
current from the inverter can be conducted to a high frequency transformer, whereas the
output voltage of the high frequency transformer is in the range of 1kV to 12kV and
then the output current is the multiplied by a voltage multiplier such as a hexuplicator of
the Cockroft-Walton type. Alternatively, the output from the inverter can be fed directly
to the voltage multiplier. The multiplier makes it unnecessary to utilize higher voltage
transformers, which out up a high demand on electrical insulation of the coiling wires
and the connection wiring. The output of the hexuplicator is then conducted to the
electrodes for electrical weeding.
A different topology for the electronic converter proposed before can be made
for monophasic circuits, as shown in Fig. 1. The invasive plant may be represented as a
variable resistive load from the electric/electronic point of view, as already justified
before.
The topology elements are listed below:
- a power source, such as the power grid or a generator;
- a rectifier or rectification bridge if the power source is AC;
- an inverter such as a half-bridge or full-bridge inverter;
- a capacitive and/or inductive harmonic filter;
- a high frequency transformer;
-a capacitive voltage multiplier.
For example, with the use of a voltage doubler as the voltage multiplier fed by
the transformer’s secondary, the isolation issues for the transformer’s high voltage
operation is reduced, as well as the number of turns necessary to achieve the desired
voltage levels, facilitating the transformer’s construction and reducing its size, weight
and volume, that were already reduced for the high frequency operation.
Adjusting the inductor and/or inductive/capacitive filter value so the inverter’s
IGBT can work with resonant switching reduces its conduction losses and increases the
converter’s efficiency. The IGBT’s resonance frequency is tuned as the resonance
between the external inductor and the total capacitance reflected to the transformer’s
primary or directly to the voltage multiplier, considering the effects of the variable load
and the voltage multiplier.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained with reference to the drawings. It is to be
understood that the drawings are for reference only and are not to be considered limiting
of the invention. In the drawings, wherein similar reference numerals constitute similar
elements:
Fig. 1 shows a diagram of the circuit providing the current for the weeding
device;
Fig. 2 shows an alternative embodiment of the circuit;
Fig. 3 shows another alternative embodiment of the circuit; and
Fig. 4 shows yet another alternative embodiment of the circuit.
DETAILED DESCRIPTION OF THE DRAWINGS
An example of the circuit providing the current for the weeding device is shown
in Fig. 1.
The example topology as shown in Fig. 1 can be improved by using a high order
voltage multiplier at the transformer’s secondary, as a voltage hexuplicator, as shown in
Fig. 2. A high order multiplicator simplifies even more the transformer’s construction,
using the same justifications as before. The impedance matching happens in the same
way as described by the converter with the voltage doubler, but in the topology
presented below the power coupling range can be extended.
The external inductor reflected to the transformer’s secondary side will also
provide an impedance matching with the voltage doubler series impedance, and this
association with the “plant resistance” will be seen by the transformer as a resistance in
parallel with a capacitor inversely proportional to this resistance value. The output
voltage will be variable with the resistive load, once the voltage doubler capacitor
charging will be “controlled” by the total series impedance seen by him, like that
different power values will be delivered by the converter, depending on the resistive
load, according to the basic power equation = , where R, V and P are the
resistive load, its voltage and its power dissipation, respectively. As the impedance
matching happens in self-adjustable way, this converter topology presents a self-
adjustable power control without the necessity of a control strategy implementation.
The impedance seen by the transformer is still a resistance in parallel with a
variable capacitor, as described before. The inverter’s resonance switching can be tuned
so the converter delivers the optimum maximum power to a specific impedance value.
The output power is variable for the same reason as described for the voltage doubler,
but for different orders voltage multipliers, all the multipliers capacitors charging must
be taken in consideration.
The voltage multiplier series impedance partially solves the problem of
transformer series resonance excitation, once the transformer’s secondary is never in a
real open circuit situation with this new topology.
When the resistive load tends to a low value (short-circuit situation), the voltage
multiplier presents a series impedance reflected to the primary that, associated with the
external inductor, protects the transformer against high short-circuit currents. When the
load tends to a high value (open circuit situation), all the capacitors of the voltage
multiplier are charged, increasing the secondary voltage peak, but still limiting it to a
maximum value equals the multiplier stage (6, in the case of the hexuplicator).
Another strategy to protect the transformer against this dangerous operation is
the addition of an adequate capacitive or a capacitive inductive filter after the external
inductor, as shown in Fig. 3 and Fig. 4. As the filters can be projected to remove the
high order harmonic components from the transformer’s input voltage, the series
resonance excitation can be avoided with this strategy.
As the “plant resistance” deviates from the tuned value, the delivered power
decreases from its optimum maximum value, but a considerable range of power values
is still delivered to a great variety of resistive loads, as can be seen in Table below, that
show the power delivered to different values of resistive loads, considering power grid
as power supply and a capacitive voltage hexuplicator. It’s important to notice that the
electronic converter as described was never used before for the invasive plant control.
Power Variation with the Resistive Load (2.77 a 100 kΩ)
Power Grid Voltage
Value 220 V 127 V
Current RMS Active Current RMS Active
Resistive Load (kΩ) (A) Power (W) (A) Power (W)
100 1.25 270 1.3 165.1
75 1.55 334.8 1.64 208.28
50 2.2 475.2 2.29 290.83
3.05 658.8 3.33 422.91
12.5 2.23 481.68 2.55 323.85
8.5 1.75 378 2.04 259.08
6.25 1.47 317.52 1.7 215.9
1.09 235.44 1.46 185.42
3.57 0.929 200.664 1.18 149.86
2.77 0.838 181.008 1 127
The electronic converter as described before is optimized for monophasic low
and medium power applications, so it’s ideal for manual applications, nevertheless the
topology can be adapted for high power applications, using high power sources, as DC
or tri-phasic sources, and tri-phasic rectifiers, as already described in the other
topologies.
In this case maybe a full-bridge inverter can be more adequate to deliver power
levels necessary. Another modification that can be interesting for high power
applications is the used of high frequency transformer with a centered tap at its
secondary winding, as shown in Fig. 5. The centered tap “divides” the secondary
isolation issues and increases the transformer safety. The voltage multiplier can still be
used, but now in a duplicated way, as shown in Fig. 5.
As a general description of the system, a DC or AC power supply of any number
of phases generates a voltage. This voltage is fed to an inverter that increases frequency.
The current with increased frequency is fed to a harmonic filter (inductive, ca-pacitive
or both) that ensures a high power-factor, diminishing or excluding the need of a
separated PFC. The inductive and/or capacitive harmonic filter may feed a high
frequency transformer that further increases the voltage input for the voltage multiplier.
The high frequency transformer may comprise a centered tap at its secondary winding,
which can serve as a voltage reference or grounding to the secondary coil. The output of
the previous components is fed to a voltage multiplier, such as a voltage multiplier of
the Cockroft-Walton type or a full wave Cockroft-Walten type, such as a hexuplicator,
multiplying the input voltage by a factor of six. The voltage multiplier provides
different voltage levels depending on its load, so for a variable load it makes an auto-
adjustable power control without any additional circuitry, processor or controller
necessity. If, as described, a transformer was necessary to further increase the voltage
be-tween the harmonic filter and the voltage multiplier, the voltage multiplier always
represents a series impedance connected at the transformer secondary, not letting the
transformer in a direct real open circuit situation, reducing the risks of series resonance
excitation and voltage peaks that could damage insulation or create other internal
damages.
This particular construction allows for the inverter switching to be set as
resonant or quasi-resonant. This setting of the inverter as resonant or quasi-resonant,
reduces its output harmonic composition, reducing the risk of transformer series
resonance excitation and, consequently, reducing the risk of compromise the
transformer insulation. Also, the inverter’s switches (like, but not limited to IGBTs,
power transistors, mosfets) have reduced conduction losses when working in the
resonant or quasi-resonant mode, increasing the converter’s overall efficiency.
In Fig. 1 the sinusoidal voltage from the power supply 1 is rectified by the full-
wave rectifier 2 and produces a pulsed DC voltage which is provided to the half-wave
inverter 3. A high-frequency square-wave voltage is then produced by the half-wave
inverter 3 and provided to the voltage amplification block (the external inductor 4 and
the high-frequency transformer 5). The amplified voltage provided at the output of the
high-frequency transformer 5 is duplicated by the voltage doubler 6 and applied at the
variable resistive load 9 through the electrodes 7 and 8.
The topology of Fig.2 works exactly at the same way of Fig.1, but the voltage at
the transformer’s output is now multiplied by 6, by the voltage hexuplicator 10. As with
Fig. 1, the resistive load receives a higher output voltage through the electrodes 11 and
12. In this topology, a lower voltage ratio transformer can be used, for the same
applications when compared to the topology of Fig. 1.
In Fig. 3 the capacitor 13 is added to the topology of Fig.1, to filter undesired
harmonic components at the transformer’s input voltage and the high-voltage is
delivered to the load through electrodes 14 and 15. In Fig.4 an inductive-capacitive
(LC) filter 16 is used for the same function and the load receives the output voltage
through the electrodes 17 and 18.
Fig. 5 shows an adaptation of the topology of Fig.1 for three-phase systems. The
three-phasic full-wave rectifier 20 is fed by the three-phasic power supply 19 and
provides its output for the full-wave inverter 21, which works at resonant or quasi-
resonant switching, to reduce the inverter’s switching losses. The high-frequency
transformer 22 now have a centered tap at its secondary side to reduce the secondary
voltage stress, once the secondary voltage is normally higher in three-phasic
applications. The voltage multiplier 23 is double doubler and is connected in the
symmetric way shown in Fig. 5, delivering the high-voltage to the plant resistance
through the electrodes 24 and 25.
Although only a few embodiments of the present invention have been shown and
described, it is to be understood that many changes and modifications may be made
thereunto without departing from the spirit and scope of the invention.
Claims (13)
1. A weed inactivation device, comprising: at least two electrodes, a DC or AC power supply, and an electro-electronic converter topology configured for supplying current to the at least two electrodes, comprising at least two of the following components: an inverter, an inductive and/or capacitive harmonic filter, or a capacitive voltage multiplier composed of diodes, wherein the weed inactivation device is constructed alone or in parallel with stages that work together to control invasive plants by electrocution, and wherein at least one of the electrodes is configured to be directed to the weed.
2. The weed inactivation device according to claim 1, further comprising an inverter that is fed by the power supply and is configured to feed the inductive and/or capacitive harmonic filter.
3. The weed inactivation device according to claim 1, further comprising a high frequency transformer that is configured to receive an output of the components.
4. The weed inactivation device according to claim 1, further comprising a voltage multiplier that is configured for receiving an output of the components, the voltage multiplier providing different voltage levels depending on its load.
5. The weed inactivation device according to claim 2, wherein the inverter has switching that is set to be resonant or quasi-resonant.
6. The weed inactivation device according to claim 1, wherein the power supply comprises an AC current supply having a frequency in the range of 30 Hz to 90 Hz, and further comprising a full-wave rectifier that is configured to rectify the AC current, creating pulsed DC current that is double a frequency of the AC current.
7. The weed inactivation device according to the claim 6, further comprising a capacitor that is configured to damp the pulsed DC current, the capacitor being switched parallel to an output of the full-wave rectifier.
8. The weed inactivation device according to the claim 7, further comprising a half-bridge inverter that is configured to switch the pulsed and damped DC current to create a rectangular AC current of higher frequency than the pulsed and damped DC current.
9. The weed inactivation device according to claim 8, further comprising a high frequency transformer that is configured to receive an output of the half-bridge inverter to create a higher voltage than input from the half-bridge inverter.
10. The weed inactivation device according to claim 9, further comprising a cooling sink or cooling blades that are configured for passively cooling the high frequency transformer.
11. The weed inactivation device according to claim 9, wherein the high frequency-transformer comprises a centered tap at a secondary winding.
12. The weed inactivation device according to claim 11, wherein between a first pole of the secondary winding and the centered tap and between a second pole of the secondary winding and the centered tap the pulsed DC current is multiplied by a capacitive voltage multiplier.
13. The weed inactivation device according to claim 12, wherein the voltage multiplier is a hexuplicator that is configured for multiplying the input voltage by a factor of six.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE102018003199.4 | 2018-04-19 |
Publications (1)
Publication Number | Publication Date |
---|---|
NZ752542A true NZ752542A (en) |
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